Geology - Geological Modeling

Natural Fracture Systems and Fractured Hydrocarbon Accumulations, Mechanics and Management

 

Instructor

  Dr Dirk Nieuwland (NewTec International, Leiden, Netherlands)

Duration

  2 days

Disciplines

  Geology – Geological Modeling

Level

  Intermediate

Language

  English

EurGeol

  10 CPD points

Keywords

 
 3D   CLAY   DRILLING   FAULTS   FRACTURES   HIGH‑RESOLUTION   SHALE   SHALE GAS   UNCONVENTIONAL   WELL LOG 

 

Course description

In this short course a geomechanical approach to the prediction of the location and orientation of open and closed fractures will be discussed. Fractures are discontinuities in brittle rocks that are the result of failure of the rocks. The mechanical rock properties and the failure conditions determine whether the type of failure is an open or closed fracture. Geomechanically, joints are large examples of tension fractures and faults are large examples of shear fractures. Tension fractures are always open when they form and it is this property that makes these small discontinuities so important for the exploitation of oil and gas from tight reservoir rocks. Prediction of the location and orientation of open fractures is complicated by the small size of fractures. They are so small that they are below the detection limit of many of the commonly used tools such as well logs or seismic. Fracture detection by seismic methods is basically impossible but some high-resolution logging tools can detect fractures if the circumstances are suitable. If both logs and seismic cannot detect fractures, geomechanical modelling is often turned to as the last resort. However, it is often possible to apply basic geomechanics with success, without having to rely on sophisticated software. A major disadvantage of high end software is, that such programs require a vast amount of detailed input. Such detail is not always available. Even when sufficient detailed data are available, it is a major effort to generate the required input for the software. The advantage of an analogue approach is that it can be done with much less data, quicker and a lot cheaper. The result will of course be in less detail than that of 3D geomechanical output but the cost-effectiveness of an analogue (analytical) approach is high and the 'first pass results' provide a good and reliable basis for further work.

This short course presents the fundamental geomechanics that is required to achieve a sound understanding of natural fracture systems, to predict the basic elements of natural fracture systems and to extract the wealth of information that is contained in natural fault and fracture systems, to the benefit of further development of naturally fractured systems. The term ‘reservoirs’ has been deliberately avoided, because unconventional hydrocarbon accumulations such as found in tight reservoirs or shales, do not form ‘reservoirs’ in the classic meaning of the word. This is particularly so in shales, where the gas that is contained in the shales is adsorbed to clay minerals and cannot flow naturally. In such unconventional hydrocarbon systems, geomechanics is often the last and only resort to predicting attractive drilling locations, orientations and well stimulation such as hydraulic fracturing. A newly developed demonstration experiment will be used to illustrate the development of intersecting tension fracture systems.

 

Course objectives

Assess the possibilities to approach the exploration and development of unconventional hydrocarbon systems. These can be shale gas systems, other forms of tight reservoirs or fractured crystalline basements.

 

Course outline

The course will begin with an introduction to geomechanics as the basic 'tool' to understand natural fracture systems and naturally fractured unconventional hydrocarbon systems. Natural fracture systems and the associated properties will be considered. Boundary conditions of artificial hydraulic fracturing will be discussed, with the exception of details of the hydraulic fracture design, which does not form part of this course.

Case histories of tight and unconventional reservoirs will be presented for discussion.

Participants are strongly recommended to bring their own case examples for treatment and discussion as this will enable immediate application of the course content to the current work environment of the participant.

 

Participants' profile

Geologists, geophysicists and reservoir engineers who work with faulted and fractured reservoirs will benefit from this short course. The topic is relevant for exploration as well for production. A recent expansion of the course topics includes exploration and development of shale gas systems.

 

Prerequisites

Participants should have knowledge of general geology and structural geology and basic physics. A basic knowledge of geomechanics is an advantage but is not strictly required.

 

About the instructor

Dr Dirk Nieuwland

Prof. Dr Nieuwland has 39 years of experience as a geologist, including 35 years in oil and gas exploration and production. He has published numerous papers in this field and edited two books in the Special Publication series of the Geological Society of London.

One of NewTec's geo-mechanical field models resulted in adding a billion bbls of oil to the reserves of a tight naturally fractured oil reservoir, including accurate prediction of open fracture locations and orientation, in-situ stresses and reservoir quality. Other models have successfully guided exploration, appraisal and development in complex geological settings, including a world first successful prediction of open fractures in a fractured oil bearing crystalline basement.

 

Recommended reading

Any structural geology textbook will give sufficient background knowledge to follow this short course successfully.

 

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